.508 Square Shafts. w being exerted through 2?r feet at every revolution: rT ^ H.P.= X 27T N s 7T ^8 27T N x - 33000 12x16 33000 320^10 _.. = ^320810 _ __ tJ p .—: 68-44 J. H.P. V7VN Example 47.—A shaft transmits 20 H.P. at 160 revs. Find (i) how many H.P. it will transmit at 250 revs., and (2) dia. to transmit 40 H. P. at 250 revs, withy at 2 tons per sq. in. for stiffness. (0 (2), H.P. ex /. 20 oc loo and H, P. req. a 250 100 : 20 : : 250 : H. P. and H. P. = 50 d= 68'44 40 2x2240x250 =2-215 Ex-ample 48.— Compare the weight of shafting in a twin with that iri a single screw ship, neglecting couplings: the H.P. in each being the same and the speed of each twin being 25 °/e above that of the single screw. (Hons. Mach, Constr, Ex., 1886.) d oc _ "H P ' ... a i for single shaft ... oc 73 for each twin shaft. - « i for single shaft ... « screws. Square Shafts are often adopted in travelling cranes. In Fig. 490, B Is the longitudinal and A the CTOSS girder of a crane, the power being given from shaft D through mitre gear to F, and by spur gear to G. As the carriage moves along B, the tumbler bearings are turned through a right angle, and are only off the shaft during the passage of the rnitre wheels, the bracket at B being shaped to serve as a tappet.